Patient identification marker apparatus



June 30, 1970 H. T. FINCH ET AL PATIENT IDENTI IFICATION MARKER APPARATUS 3 Sheets-Sheet 1 Filed May 17, 1968 M 6 5 M 2 M wm a WM 5 m u 6 0 6 I am 0 C A .11 n z w 4 D J n n n a M n f K 0 r A. w c u x a u v 2 @6 5 W A u M" n W "f g n S M o 4 o 0 r n a u T 5 W w m m m m M m u mo 2 cm .5 n j Rm m M F+L m a 1. l 2 n W m W m n 6p Mp M 2 FROM INVENTOR BY f g 4TTO/Q/VAJV H, T. l cH ET AL 3,517,662

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June 30, 1970 Filed May 17, 1968 Jun 30, 1970 H. T. FINCH ET L 2 PATIENT IDENTIFICATION MARKER APPARATU:

Filed May 17, 1968 3 Sheets-Sheet 5 MAR/5? (OA/TROA C/ACU/7 204 mvamoa 4770A M y United States Patent 3,517,662 PATIENT IDENTIFICATION MARKER APPARATUS Horace T. Finch, Arcadia, and Donald L. Emmons, Rowland Heights, Calif., assignors to The Birtcher Corporation, Los Angeles, Calif., a corporation of California Continuation-in-part of application Ser. No. 624,007, Mar. 17, 1967. This application May 17, 1968, Ser. No. 730,003

Int. Cl. A61b 5/04 US. Cl. 1282.06 6 Claims ABSTRACT OF THE DISCLOSURE In a patient monitoring system, a central station sequentially monitors ECG signals from a plurality of bedside stations. When the central station dwells on an input from a patient having an abnormal pulse rate, operation of a marker generator and a marker control circuit is initiated. The marker generator produces square wave pulses until disabled by the marker control circuit; the number of pulses generated is indicative of the particular patient being monitored. A single ECG associated with the central station prints out the square wave pulses followed by the ECG pattern of the patient having the abnormal condition, the recorded marker pulses thus serving to identify the ECG trace.

The present application is a continuation-in-part of co-pending application Ser. No. 624,007, entitled Medical Monitoring System, filed Mar. 17, 1967.

BACKGROUND OF THE INVENTION The present invention relates to a patient identification marker apparatus for use in an automatic medical monitoring system. More particularly, the invention relates to an apparatus for providing patient identification indicia directly on the print out of a single electrocardiograph used to transcribe sequentially the ECG patterns of a plurality of patients being monitored by the system.

It is common in present day medical monitoring systems to evaluate automatically various physiological characteristics of a plurality of intensive care patients. Typically, when certain functions, such as pulse, respiration rate, blood pressure, temperature, etc., exceed safe limits, the abnormal condition is sensed, an audible warning signal sounded and a light turned on to identify the patient in distress.

More complete medical monitor systems such as that described in our co-pending application, Ser. No. 624,007, entitled Medical Monitoring System, include one or mo re devices such as an electrocardiograph (ECG) to record the condition of the patient. In such systems, a central switch detects an alert signal indicative of abnormal patient condition and initiates operation of the ECG. Should two or more alert signals be detected, the switch causes sequential transcription of the electrocardiographic signals of each patient in distress.

A limitation of such prior art medical monitoring systems is that the ECG print out may contain consecutive cardiac patterns of several patients, with no indentification marks attributing each pattern to a specific patient. This particularly is a problem in systems wherein unattended ECG operation is initiated automatically by the monitor. At best the problem complicates the job of medical record keeping; at worst it could result in incorrect diagnosis were a particular ECG pattern attributed to the Wrong patient.

The present invention provides a marker apparatus, adapted for use with a medical monitor system, which 3,517,662 Patented June 30, 1970 identifying the patient whose cardiac pattern follows on the chart.

SUMMARY OF THE INVENTION This invention relates to a medical monitoring system and, in particular, to a cardiac monitoring system wherein a plurality of bedside systems continuously transmit the patients electrocardiographic (ECG) signals to a central monitoring station, where the signals can be sequentially monitored. As each patients signal is monitored, a white light is illuminated in the central station to identify the patient. If any patients heart beat rate is above or below prescribed limits, a red light is auto matically illuminated: at the central station, and an audible alarm signal can be energized. Also, an 'ECG is activated at the central station to provide a permanent recording of the distressed patients ECG trace. The inventive patient identification marker apparatus auto matically inserts a series of square waves onthe ECG chart, the marks clearly identifying which patients ECG trace has been recorded.

If there are no alarm signals received from any of the bedside stations, the central station is in stand-by condition, even if it is in the automatic mode of operation, and does not cycle through the signals received from the various patients. However, if the system is in the automatic mode, receipt of an alarm signal from any one or more of the patients will cause the central station system to start cycling through all of the patients ECG signals sequentially. Each time a distressed patients sig nal is received, the red light corresponding to the patient is illuminated and his ECG signal is recorded for fifteen seconds, or some other time period, as desired. A patient identification mark also is recorded on the ECG chart. After that time period has expired, the station sequentially steps through the remaining bedside stations to determine if there are other distressed patients. If so, it will stop and monitor that bedside station for the predetermined length of time, and then move to the next station. If there are no distressed patients, the central station will then remain in stand-by until another emergency occurs.

In manual operation, an operator can manually step the central station monitoring process through the various bedside stations, and record electrocardiographic traces for any length of time desired for any of the patients. As previously noted, ECG signals are received at the central station at all times from all patients, even though they are not all recorded.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, wherein like numerals designate like components, and in which:

FIG. 1 is a block diagram of a system embodying the invention;

FIG. 2 is a perspective view of a central station .switch for monitoring up to five patients;

FIG. 3 is a circuit diagram of the switch shown in FIG. 2;

FIG. 4 is an electrical schematic diagram of an embodiment of the inventive patient identification marker apparatus configured for use with the switch shown in FIG. 2; and

FIG. 5 illustrates a typical ECG strip chart recording including patient identifying indicia generated by the apparatus of FIG. 4.

The system described herein is adapted to monitor the heart beats of five patients in an intensive care ward. However, the system is open-ended and may be adapted to monitor any number of patients up to a reasonable limit. Therefore, the invention is not to be considered as limited to monitoring any particular number of patients.

FIG. 1 illustrates a block diagram of a monitoring system embodying the invention. Each bedside station (only one of which is shown) comprises a sentinel unit 12, which provides signals to a bedside oscilloscope 14 and to a monitor switch 16 in a central station 18. The signals provided from the bedside station 10 are representative of a particular patients ECG condition and, if the patients heart beat is above or below predetermined limits, an alarm signal is also transmitted to the central station. The switch 16 in the central station provides signals to a monitor oscilloscope 20 and to an electrocardiograph 22 if desired. Of course, only one bedside station can be monitored at one time. Patient identification marker apparatus 23 provides a marker signal to ECG 22, which signal is recorded on the ECG chart to identify the patient whose cardiac pattern follows on the chart.

The sentinel 12 in each bedside station emits a continuous signal representing the particular patients ECG and an alarm signal if the patients heart beat rate falls below or goes above predetermined limits. Although the invention is not limited to the use of any particular unit, the Model 40 2 Sentinel manufactured and sold by The Birtcher Corporation, Los Angeles, Calif., is well suited to the application. That unit contains a meter, which visibly indicates the patients heart beat rate, and also contains high and low limit switches. Along with the ECG signals, this unit provides an 18 volt signal to the central station indicating an alarm condition when the lower or upper limits of heart beat rate are exceeded, indicating a bradycardia or tachycardia condition in the patient.

The Oscilloscopes 14 and 20 may, if desired, each be a Model 401 Monitorscope and the electrocardiograph 22 may be a Model 409/335 Electracardiograph, both of which are manufactured and sold by The Birtcher Corporation of Los Angeles, Calif. However, the invention is not limited to the use of any particular Oscilloscopes or electrocardiographs.

FIG. 2 is a perspective view of the exterior of the central station monitor switch 16. As shown, the switch 16 embodies on its front panel a plurality of red lights 24a-24e, which, if illuminated, indicate one or more distressed patients. Its front panel also contains a plurality of white lights 26a-26e, each of which, when illuminated, indicates, a particular patient being monitored. Only one of the white lights 26 can be illuminated at one time, whereas a plurality of red lights 24 can be simultaneously illuminated, if a plurality of patients are in distress. The switch 16 also has on its front panel a power on-oif switch 28, an ECG run switch 30 and a selector switch 32. The functions of the latter two switches will become apparent from the description of the circuit diagram of FIG. 3. It is sufficient for the moment to say that both the ECG run switch and the selector switch 32 are spring biased toward the automatic position, and can only be manually depressed to the manual position to cause the switch 16 to set one position for each depression of the switch 32, regardless of how long the switch is held in the manual position.

Although FIG. 2 illustrates a monitor switch adapted to receive signals from five patients, as does the schematic diagram of FIG. 3, it is pointed out that the system of the invention is open-ended, and any number of input signals can be accommodated with minor modifications to the system, without departing from the invention.

FIG. 3 is a circuit diagram of the monitor switch 16. As shown, it embodies a power supply 34 that provides +50 volts direct current and +27 volts direct current on 4 lines 36 and 38, respectively, while a line 40 serves as the return.

Connections are made from the various bedside sta tions 10 shown in FIG. 1 to input terminals 44, 46, 48, 50 and 52 in the monitor switch 16. These terminals receive +18 volt alert signals if one or more patients are in distress; if no patients are in distress (that is, too slow or too fast heart beat rates), no signals are present on terminals 4452. The terminals 4452 are respectively connected to energize the red lights 24a-24e located on the front panel of the switch 16, if signals are received from the sentinels 12 in any of the bedside stations 10. One side of each of the lights 24a24e is connected to one of the terminals 4452, and the other sides of the lights are respectively connected through resistors 54-62 to the return line 40.

A plurality of NPN transistors 64, 66, 68, 70 and 72, equal in number to the number of patients being monitored, are provided, with the bases of the transistors being respectively connected through resistors 74, 76, 78, '80 and 82 to the junctures of the lights 24a-24e and resistors 54-62. Thus, when any one of the lights 24a24e is energized, the voltage on the base of the corresponding NPN transistor will rise and bias that transistor into saturation. The transistors 64-72 serve primarily as switches to energize an operating coil 84a of the two-section relay 84. The relay has two sets of contacts 84b and 84c, which are normally open when the relay is de-energized. One end of the relay coil 84a is connected to all of the collectors of the transistors 74-82, and the other end of the relay coil is connected to the power supply line 38 (+27 v.). A diode 86 is connected across the relay coil 84a. The emitters of all of the transistors 64-72 are connected to the return line 40.

'One of the more important elements of the monitor switch 16 is a five-deck, five-position switch 90, having decks 90a-90e (for monitoring five patient bedside stations). The switch 90 is stepped through its five positions by a stepping relay coil 92, which is energized through a two-position section 92a, as will be hereinafter described, which is normally in position to energize the relay coil 92 from the power line 36 (+50 v.). The relay coil 92 is paralleled by a diode 93 and a varistor 95. In order for the relay coil 92 to be energized, a silicon controlled rectifier 94, connected between the bottom end of the coil and the return line 40, must be conducting. This action will be described later.

The input terminals 4452 are respectively connected to the five contacts of the switch deck 90a. The rotor of the deck 90a is connected through normally-closed contacts 96a of a relay 96 and through a resistor 98 to the base of an NPN transistor 100. A capacitor 102 is connected across the coil 96b of the relay 96.

The contacts of the second deck 90b of the switch 90 are respectively connected to the return line 40 through the white lights 26a-26e, and the rotor of the section 90b is connected to the power supply line 36 through a series regulating transistor 206. The base of transistor 206 is maintained at a constant voltage by a Zener diode 208, current to which is supplied via a resistor 210. As the rotor of the section 90b steps from one position to another it causes the white lights 26a-26e to be sequentially illuninated, thus indicating which patient is being monitore Sections 90c, 90d and 90a of the switch 90 serve to provide ECG signals from a particular bedside station to the central station. These signals are provided, for example, on terminals 104, 106 and 108 respectively to one contact on each of the sections 90c, 90d and 90e from a first patient and the rotors of those sections provide these signals to output terminals 110, 112 and 114. These signals may be provided to the oscilloscope 20 and the ECG 22 shown in FIG. 1. The switch 90, in this case, serves only as a selector and performs no other function. Of course, ECG signals from other bedside stations are supplied to other contacts of the switch sections 90c, 90d and 902, so that as the switch 90 is stepped through its various positions, the ECG traces of the patients are successively monitored and displayed on the oscilloscope 20 and/or permanently recorded on the ECG 22.

In automatic operation, timing of the successive monitoring of patients is controlled by the timing circuits embodying transitstors 120 and 126. It, in turn, is controlled by the silicon controlled rectifier 94 and by transistors 100, 116, 118, 120, 122, 124 and 126. The transistors 100, 116, 118, 122 and 124 are NPN type, while the transistors 120 and 126 are uni-junction transistors. Of course, the particular types of transistors used are matters of design choice, and the invention is not limited to the use of any particular type or types.

The base of the transistor 100 is connected through a resistor 128 to the power supply return line 40. The collector of that transistor is connected directly to the power supply line 38 (+27 v.). The emitter of the transistor 100 is connected to the base of the transistor 116 through a capacitor 130 and a diode 132. The juncture of the capacitor 130 and the diode 132 is connected to the return line 40 through a resistor 134, and the base of the transistor 116 is connected to the return line through a resistor 136.

The transistors 116 and 118 comprise a bistable flipflop, with the collector of the transistor 116 being connected to the base of the transistor 118 through a resistor 134 and the collector of the transistor 118 being connected to the base of the transistor 116 through a resistor 136 The collectors of the transistors 116 and 118 are respectively connected through resistors 138 and 140 to a line 142, which is connected through a resistor 144 to the power supply line 38. The emitters of the transistors 116 and 118 are connected directly to the power supply return line 40.

The base of the transistor 118 is connected to all of the collectors of the transistors 64-72 through a diode 143 connected in series with a resistor 145. The base of the transistor 118 is also connected to one terminal 120a of the uni-junction transistor 120 through a diode 146 and a capacitor 148. A resistor 150 connects the base juncture of the diode 146 and the base of the transistor 118 to the return line 40, and a resistor 152 connects the juncture of the diode 146 and the capacitor 148 to the same line. The terminal 120a is also connected to the return line 40 through a resistor 154.

The emitter 12% of the uni-junction transistor 120 is connected directly to the collector of the transistor 122, to the supply line 142 through a resistor 154 serially connected with a rheostat 156, and to the return line 40 through a capacitor 158. The resistor 154, rheostat 156 and capacitor 158 determine the rate at which the stepping relay 92 operates, as will be later described.

The emitter 12% of the uni-junction transistor 120 is also connected to the collector of the transistor 122, and its electrode 120c is connected to the line 142 through a resistor 159. The emitter of the transistor 122 is connected directly to the return line 40, and its collector is connected to the juncture of the resistor 154 and the capacitor 158, and, as stated, to the emitter of the unijunction transistor 120.

The emitter of the transistor 124 is connected to the base of the transistor 122 through serially connected resistor 160 and diode 162 and thence to return line 40 through resistor 164. The collector of the transistor 124 is connected directly to the power supply line 38 and to the collector of the transistor 100. The base of the transistor 124 is connected directly to the collector of the transistor 11-6. The emitter of the transistor 124 is also connected to one contact of the section 84b of the relay 84. The other contact of the section 84b is connected through a resistor 166 to the return line 40, and through a rheostat 168 and a resistor 170 to the emitter of unijunction transistor 126 and thence to the return line 40 through a capacitor 172. One electrode of the transistor 126 is connected to the supply line 38 through the resistor 174, and the other electrode is connected to the return line 40 through a resistor 176. The top (as seen in FIG. 3) of the resistor 176 is connected through capacitors 178 and 180 to the pole of the automaticmanual switch 32. A resistor 182 is connected between the pole of the switch 32 and the return line 40. It is pointed out that the automatic contact on the switch 32 is unconnected, whereas the manual contact is connected to the supply line 38.

The gate electrode 94g of the silicon controlled rectifier 94 is connected to the juncture of the capacitors 178 and 180. It is also conncted to the return line 40 through a diode 184 and a resistor 186 connected in parallel. A capacitor 188 is connected between the lines 142 and 40 to act as a filter.

An NPN transistor 190 has its. base connected to the collector of the transistor 118, and its collector is connected to the supply line 38. Its emitter is connected through the contacts of relay section 84c and through switch 30 to a terminal 192. When the switch 30 is in automatic position, the transistor 190 will provide a voltage, at appropriate times, on the terminal 192 to energize an oscilloscope, an ECG or an audible alarm. When the switch 30 is in manual position, the supply line 38 is connected directly to the terminal 192 through a resistor 194.

In operation, when no alert signals are being received from the bedside stations, transistors 64, 66, 68, 70, 72, 100, 116, 120, 126 and silicon controlled rectifier (SCR) 94 are non-conducting. Thus, the coil 84a of the relay 84 is not energized and the contacts 84b and 840 are open. In this state, the transistor 124 is conducting as are the transistors 118 and 122. In this condition, the coil of stepping relay 92 is unenergized because the SCR is non-conducting. Hence, the switch will remain in a fixed position.

If a +18 volt alarm signal is received on any of the terminals 44-52, it causes one of the red lights 24a24e to light, which biases one or more of the transistors 64-72 into saturation. This energizes the coil 84a of the relay 84 and causes the contacts 84b and 840 to close. When the contacts 84b close, it supplies a bias voltage to the transistor 126, which biases the unijunction transistor into conduction. The transistor 126, rheostat 168, resistor 170 and capacitor 172 comprise a pulse generator, which supplies pulses through the capacitor 178 to the control electrode 94g of the SCR 94. The repetition rate of the pulses is determined by the setting of the rheostat 168 and is normally set at approximately 0.4 second.

As each pulse is received by the SCR 94 from the transistor 126, the relay 92 is energized. When the relay 92 is energized it mechanically loads a spring (not shown), which moves the switch 90 one step. The relay coil 92a is energized through contacts 92b from the supply line 36. Thus, when the relay 92 is energized, the contacts 92b connect the supply line 36 to the coil 96a of the relay 96.

When the normally-closed contacts 96a of the relay 96 open, they disconnect the 'base of the transistor from the rotor of the switch section 90a and the transistor 100 remains in its non-conducting state. At this time, the contacts 92b have de-energized the coil 92a of the relay 92. The anode supply voltage for the SCR 94 is thus broken and SCR 94 is turned off. This de-energized the coil 92a of the relay 92 and the contacts 92b return to the position shown in FIG. 3. The SCR 94 and the relay 92 are again energized when the next pulse is received from the transistor 126.

If, when the contacts 96a are closed, the base of the transistor 100 receives a positive alarm voltage from the rotor of switch section 90a, it will be biased into conduction and supply a pulse through capacitors and diode 132 to the base of flip-flop transistor 116 to bias it into conduction. When the transistor 116 conducts, it reduces the bias on both transistors 118 and 124 and causes them to be non-conducting. When the transistor 124 is not conducting, it can no longer supply voltage to the bias network comprising transistor 126 and SCR 94 so the stepping relay coil 92 will be de-energized and the relay will remain in its last position. At this time, both a red and a white light are illuminated along with sounding an audible alarm, if desired.

When the transistor 118 is cut off, the transistor 190 is biased into conduction to supply a signal through the contacts 84c of the relay 84 to the output terminal 192 to turn on external equipment such as an ECG, oscilloscope or alarm.

With the transistor 122 non-conducting because of lack of base bias, the capacitor 158 will charge at a rate determined by the values of the rheostat 156, the resistor 154 and its own impedance value. After a predetermined length of time, as set by the time constant of the circuit, transistor 120 will conduct and transmit a pulse to the flip-flop transistor 118. This length of time is preferably set at about seconds. When the transistor 118 is biased into conduction by the pulse from transistor 120, its collector voltage drops, thus causing transistor 116 to become non-conducting. As the collector voltage of transistor 116 rises, it biases the transistor 124 into conduction.

If an alert signal is still present on any of lines 44-52, relay 84 will remain energized, contacts 8412 will be closed, and conduction of transistor 124 will result in the charging of capacitor 172 via rheostat 168 and resistor 170. When capacitor 172 has charged sufiiciently to cause transistor 126 to conduct, SCR 94 also will conduct, supplying current to advance stepping switch 90 to the next position. As described above, switch 90 will continue to advance until it reaches a position at which an alert signal is present. If only one patient is in distress, only one red light will be lit, and switch 90 rapidly will step through all positions until it once again reaches the alert position. Switch 90 will dwell at this position for another nominal 15 second period, the cardiac pattern of the patient in distress again being recorded by the ECG during this dwell time.

If more than one patient is in distress, a corresponding number of red lights will be illuminated. Switch 90 rapidly will step to the next position at which an alert signal is present, dwell at this position for a nominal 15 seconds, advance to a different position at which an alert is present, dwell there for 15 seconds, and continue in this manner as long as an alert signal is present on any line. Of course, the ECG pattern of each patient in distress will be recorded during the respective dwell time of switch 90 at each alert position.

If all alert signals should terminate during a dwell period of switch 90a, all red lights will be extinguished. However, since transistor 116 is conducting during the dwell period, current will still be supplied to relay coil 84a via transistor 116, resistor 134, diode 143 and resistor 145. Thus the control signal at terminal 192 will remain on until the end of the dwell period, thereby ensuring that the ECG signals of the patient previously in distress will be printed out for the entire nominal 15 second dwell time. At the end of the dwell period transistory 116 will stop conducting, thereby causing the contacts of relay 84 to open. Thus when transistor 124 again begins to conduct, no current will be supplied to charge capacitor 172. In this case, switch 90 will not advance, and the monitor switch will remain idle until another alert signal is detected.

To place the system in the manual mode of operation, the switch is moved to the manual position, Which connects the power supply line 38 through the resistor 194 to the output terminal 192. Thus, power is continuously supplied to the terminal 192 to energize an ECG or other external display device. In order to monitor one patient after another, the switch 32 is repetitively closed, which causes a pulse to be transmitted from the supply line 38 through the capacitor 180 and resistor 186 to the gate electrode 94g of the SCR 94. This causes the relay 92 to step the switch one step for each closure of the switch 32. Maintaining the switch 32 closed does not cause the relay 92 to be repeatedly actuated. However, the switch 90 will remain in its previous position and the external device energized (so long as the switch 30 is held in the manual position) to monitor a particular patient until the switch 32 is again actuated or the system is returned to manual operation, or is over-ridden by an alarm signal.

If, while the system is in the manual mode of operation, an alarm signal is received on one of the input terminals 44-52, the system returns to its automatic mode of operation and over-rides the manual mode. Thus, the cycle of operation previously described goes into effect.

Shown in FIG. 4 is a schematic diagram of a preferred embodiment of the inventive patient identification marker apparatus configured for use with the central monitor switch 16 illustrated in FIGS. 1, 2 and 3. Referring to FIG. 4, the marker apparatus is seen to comprise a voltage control circuit 200, a marker generator 202, and a marker control circuit 204. Voltage contol circuit 200 functions to regulate the voltages available from power supply 34 (see FIG. 3) and to supply these regulated voltages to marker generator 202 and marker control circuit 204. Marker generator 202 begins to produce a square wave output to an associated electrocardiograph 22 (see FIG. 2) as soon as selector switch 90 stops at a position at which a patient alert signal is present. The number of square waves produced by generator 202 is controlled by marker control circuit 204 so as to correspond with the identification number of the patient in distress. The square wave output from marker generator 202 is recorded by ECG 22 immediately preceding transcription of the patients heart wave, thereby providing permanent identification indicia on the ECG recording.

Referring specifically to FIG. 4, voltage control circuit 200 comprises a transistor 206, a Zener diode 208 and a resistor 210, which components also are shown for claritv in the schematic diagram of FIG. 3. The collector and emitter of transistor 206 are connected in series between the +50 volt DC line 36 from power supply 34 to the armature of deck 90b of selector switch 90. The base of transistor 206 is connected to DC return line 40 via Zener diode 208 and to the +27 volt DC line 38 via resistor 210. Voltage control circuit 200 (see FIG. 4) also comprises a. transistor 212, the collector and emitter of which are connected in series between the emitter of transistor 206 and the regulated voltage line 214 to marker generator 202 and marker control circuit 204. The base of transistor 212 is connected via a Zener diode 21 6 to DC return line 40 and via a resistor 218 to the junction (g) 'between resistor 98 and relay switch contacts 96a (see FIG. 3). A capacitor 220 connected between DC return line 40 and ground provides additional filtering for the system.

Marker generator 202 comprises a uni-junction transistor 222, the source of which is connected via a resistor 224 to regulated voltage line 214, and the drain of which is connected to DC return line 40 via a resistor 226. The gate electrode of transistor 222 is connected to DC return line 40 via a capacitor 228, and to a control line 230 from marker control circuit 204 via a fixed resistor 232 and a variable resistor 234, which resistors are connected in series. As will be described below, transistor 222 and its associated components function as a pulse generator, the pulse repetition rate of which is determined primarily by the values of capacitor 228 and resistors 232 and 234.

As may be seen in FIG. 4, the gate electrode of transistor 222 also is connected to the base of a transistor 236, the collector of which is connected directly to regulated DC voltage line 214. The emitter of transistor 236 is tied to DC return line 40 via a series connected fixed resistor 238 and a variable resistor 240. The adjustable contact on resistor 240 is connected to the base of a transistor 242, the emitter of which is connected via a resistor 244 to DC return line 40. The collector of transistor 242 is connected via the coil 246a of a relay 246 to regulated Voltage line 214. The contacts 24Gb of relay 246 are connected to output terminals 248a and 248b.

Marker control circuit 204 (see FIG. 4) comprises a uni-junction transistor 250, the source of which is connected via a resistor 252 to the regulated DC voltage line 214. The drain of uni-junction transistor 250 is connected directly to the control electrode 254a of a silicon controlled rectifier (SCR) 254 and via a resistor 256 to DC return line 40. The gate of transistor 250 is connected to DC return line 40 via capacitor 258, and to the common cathode terminal 260 of a plurality of diodes 264- 272 via a variable resistor 274. The anode terminal of each of diodes 264-272 is connected via a respective one of resistors 276-284 to terminals (a) through (e) respectively on deck 90b of selector switch 90.

The control electrode of transistor 250 also is connected directly to a collector of transistor 286 and thence through the emitter thereof to DC return line 40. The base of transistor 286 is connected to DC return line 40 via a pair of series connected resistors 288 and 290. The junction of resistors 288 and 290 is connected via a resistor 292 to the collector of a transistor 294. The emitter of transistor 294 is connected directly to regulated DC voltage line 214, and the base of transistor 294 is connected to line 214 via a pair of series connected resistors 296 and 298. The junction of resistors 296 and 298 is connected to the anode of SCR 254 via a resistor 300. The cathode of SCR 254 is connected directly to DC return line 40.

In operation, Zener diode 208, which typically may have a breakdown voltage of 15 volts and which is connected across the +27 volt output of power supply 34, maintains a constant voltage at the base of transistor 206. Transistor 206 in turn functions as a series regulator to provide a regulated voltage at the deck 90b armature contact of selector switch 90. Similarly, Zener diode 216 maintains a constant voltage level, typically 11.2 volts, at the base of transistor 212 whenever a positive voltage is present at terminal (g). Transistor 212 serves as a series regulator to provide a regulated voltage on line 214 to marker generator 202 and marker control circuit 204. Note that as described above, a voltage is present at terminal (g) only when selector switch 90 dwells at a position at which an alert is present. Thus, a regulated DC voltage appears on line 214 exactly as selector switch 90 steps to an alert position, the regulated voltage remaining on during the entire ECG recording period and terminating when selector switch 90 commences to advance to the next position.

Uni-junction transistor 222 functions as a saw-tooth pulse generator, the period of which primarily is determined by the values of capacitor 228 and the sum of fixed resistor 232 and variable resistor 234. Preferably, the values of these time-constant-control components are selected so that the generally saw-tooth output of the pulse generator has a period of about 180 milliseconds. Operation of the pulse generator is initiated as soon as a voltage is present on line 214, i.e., as soon as selector switch 90 steps to a position at which an alert signal is present.

Transistor 236 serves as an impedance matching circuit connecting the output of pulse generating transistor 222 to the base of transistor 242. The setting of variable resistor 240 preferably is selected so that transistor 242 will reach saturation approximately 100 milliseconds after the initiation of each saw-tooth pulse from transistor 222. Thus transistor 242 will be saturated for a duration of approximately 80 milliseconds during each period of the pulse generator. Saturation of transistor 242 causes relay 246 to energize, closing its normally open contacts 246a, thereby switching on a voltage applied across terminals 248a and 24812. If desired, a voltage source such as battery 302 (shown in phantom in FIG. 4) may be provided, so that the output between terminals 248a and 2480 comprises a square wave signal which will be on for milliseconds, and 0 for milliseconds during each period of marker generator 202. As will be described hereinbelow, the number of square waves produced identifies the patient in distress.

The operation of marker control circuit 204 (see FIG. 4) may be understood by recognizing that transistor 250 and its associated components also comprise a pulse generator, the period of which is determined by the values of capacitor 258, resistor 274 and a selected one of resistors 276-284. As soon as selector switch 90 reaches an alert position, a regulated voltage is supplied to marker control circuit 204 on line 214. Simultaneously, a regulated voltage is applied to one of resistors 276-284 via transistor 206 and the armature of switch deck 90b. The latter voltage begins to charge capacitor 258, via resistor 274, and when the gate threshold voltage of uni-junction transistor 250 is reached, transistor 250 begins to conduct. The resultant voltage drop across resistor 256 is sufficient to turn On SCR 254, dropping the voltage at the anode terminal 230 of SCR 254 to zero. Since the voltage at line 230 is the charging source for capacitor 228 associated with saw-tooth generating transistor 222, the square wave output of marker generator 202 is inhibited when SCR 254 begins to conduct.

Resistors 276-284 are selected to have appropriate values such that SCR 254 is turned On, and the output of marker generator 202 inhibited, after generation of a number of square waves equal to the position of switch 90. Thus resistor 276 is selected so that if switch 90 has stopped at position 1, capacitor 258 will charge sufliciently so as to turn On transistor 250 and SCR 254 after a period substantially equal to milliseconds. In this period, relay 246 will have closed only once, generating only a single square wave prior to the termination of operation of marker generator 202 due to conduction of SCR 254. Similarly, the value of resistor 278 is selected so that should switch 90 come to rest at position 2, the time required to charge capacitor 258 sufficiently to turn On SCR 254 will be approximately 360 milliseconds. Thus, the output of marker generator 202 will be inhibited after two square waves have been generated. Similarly, the value of resistors 280, 282 and 284 are selected to insure that the output of marker generator 202 will be inhibited respectively after the generation of three, four or five square Waves.

Referring again to the operation of marker control circuit 204 (see FIG. 4) conduction of SCR 254 also results in suificient voltage drop across resistor 298 to turn On transistor 294. The resultant current flow causes sufiicient voltage drop across resistor 290 to turn On transistor 286. Conduction of transistor 286 discharges capacitor 258 and ensures that capacitor 258 will not subsequently be charged until the next operating cycle of the inventive marker apparatus. SCR 254 remains conducting, and hence the output of marker generator 202 remains inhibited, until the end of the nominal 15 second dwell time of switch 90, during which dwell time the heart wave pattern of the patient in distress is recorded by associated EGG 22. When switch 90 steps to the next position, the base voltage at transistor 212 momentarily is interrupted (due to momentary opening of relay contact 96a), thereby interrupting the voltage on line 214 and turning SCR 254 Off.

To review, when selector switch 90 stops at a position at which an alert signal is present, a positive voltage appears at terminal (g) thereby turning On the regulated voltage on line 214 to marker generator 202 and marker control circuit 204. Simultaneously, one of the white lights 2-6a-26e (see FIG. 2) lights up, and a regulated voltage appears at one of resistors 27-6-284. Marker generator 202 begins to provide a square wave output. At the same time, marker control circuit 204 begins a timing cycle which results in the termination of the square wave output from marker generator 202 after a period sutficient to allow the generation of a number of square waves uniquely indicative of the patient whose ECG subsequently is to be transcribed.

The manner in which the output of the inventive patient identification marker apparatus is utilized is a matter of choice and will depend in part upon the circuitry of the particular ECG machine used. As described earlier, the ECG is turned on as soon as switch 90 comes to rest at an alert position, this condition producing a control voltage on line 192 (see FIG. 3). Simultaneously, a voltage is provided at terminal 230a (see FIG. 4) which may be utilized by the associated ECG to inhibit temporarily print-out of the ECG pattern itself. (Recall that the voltage on line 230 is present only for that duration of time during which patient identification square waves are produced by marker generator 202.) The output signal from marker generator 202, taken either across the switch contacts between terminals 248a and 24% or the square wave produced between terminals 248a and 2480, then may be used by the associated ECG to deflect its writing stylus by a slight amount either above or below the base line. This deflection results in the transscription of a series of pulses at the beginning of the ECG trace, corresponding in number to the identification number of the patient in distress. At the end of the square wave train from marker generator 202, the ECG inhibit signal on line 230 terminates, and the ECG commences to record the cardiac pattern of the patient in distress. As described above, this recording continues for a period of approximately 15 seconds (minus the time required to print the identification marks).

A typical ECG trace as may be transcribed using the inventive patient identification marker apparatus is shown in FIG. 5; in this illustrative recording, patients 2 and 5 both are in alert. Referring to FIG. 5, the initial ECG trace 310 is preceded by two square waves 312 generated by the inventive marker apparatus at the beginning of the period during which patient number 2 is being moni tored. The next ECG trace 314 is preceded by five pulses 316 generated by the inventive marker apparatus while patient number 5 is being monitored. Thus the resultant recording, produced by a single ECG operating in conjunction with the inventive automatic medical monitor system described hereinabove, includes a permanent indicia identifying each ECG trace with the specific patient being monitored. The apparatus thus overcomes a shortcoming of the prior art wherein successive ECG traces, although recorded from different patients, did not contain patient identifying indicia.

While the invention has been described hereinabove in terms of the preferred embodiment shown in schematic diagram form in FIG. 4, the invention clearly is not so limited. Thus, for example, marker generator 202 could comprise a free running multivibrator, operation of which is initiated when a central monitor switch senses a predetermined condition associated with particular patient being monitored. Marker control circuit 204 then may comprise a monostable multivibrator (one-shot) the operation of which is initiated simultaneously with that of the free running multivibrator, and which has a monostable time period indicative of which patient is being monitored. Such monstable multivibrator could be adapted to disable the free-running multivibrator at the end of the one shot period. Of course, other circuits having like functions will be obvious to those skilled in the digital circuitry art and may be substituted for marker generator 202 or for marker control circuit 204.

Although the invention has been described and illusr 12 trated in detail, it is to be clearly understood that the same is by Way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

What is claimed is:

1. A patient identification marker apparatus comprismg:

a medical monitor system adapted to detect a distress condition of a patient being monitored;

a signal generating means being actuated upon the detection of a distress condition from said medical monitor system for generating a series of pulses;

means responsive to said signal generating means for producing a pulse which is on for a portion of a period of the signal of said signal generating means and off for the remainder of said period;

means for supplying energy to said signal generating means; and

timing means responsive to the distress condition of said medical monitor system for terminating said energy to said signal generating means after a duration of time indicative of the particular patient in distress.

2. The apparatus as defined in claim 1 wherein said timing means comprises a pulse generating means, and including means responsive to the monitor system for controlling the time constant thereof.

3. The apparatus as defined in claim 1 and further comprising voltage control means for supplying regulated DC voltage to said timing means and to said signal generating means during periods when a distress condition is dected by said monitor system.

4. The apparatus as defined in claim 1 and wherein said timing means includes:

a pulse generator, and including means responsive to the monitor system for controlling the time constant thereof; and

voltage control means for supplying regulated DC voltages to said pulse generator and to said signal gencrating means during periods when a distress condition is detected by said monitor system.

5. The apparatus as defined in claim 1 and wherein said medical monitor system includes a recording means for recording a physiological condition of said distressed patient and for recording indications of said pulses prior to recording said physiological conditions toidentify the conditions with the patient.

6. The apparatus as defined in claim 1 and wherein said timing means includes:

a pulse generator, and including means responsive to the monitor system for controlling the time constant thereof;

voltage control means for supplying regulated DC voltage to said pulse generator and to said signal generating means during periods when a distress condition is detected by said monitor system; and

said medical monitor system including a recording means for recording a physiological condition of said distressed patient and for recording indications of said pulses prior to recording said physiological condition to identify the conditions with the patient.

References Cited UNITED STATES PATENTS 2,400,583 5/1946 White 128-2.06 3,199,508 8/1965 Roth 1282.06

70 WILLIAM E. KAMM, Primary Examiner 11.5. C1. X.R. 340-279 

